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Abstract:

Provided is a vitreous silica crucible which has a special region for
suppressing vibration of melt surface during pulling of a silicon single
crystal and at the same time, a marking capable of accurately monitoring
a changed position of the melt surface when passing through the special
region. The special region for preventing sloshing of silicon melt is
provided on an inner wall of a straight body portion, and the marking is
provided at least at an upper end and a lower end of the special region.

Claims:

1. A vitreous silica crucible containing silicon melt, the vitreous
silica crucible comprising: a special region provided on an inner wall of
a straight body portion, for preventing sloshing of the silicon melt; and
a marking installed at least at an upper end and a lower end of the
special region.

2. The vitreous silica crucible of claim 1, wherein the special region is
made of vitreous silica whose raw material is primarily natural silica,
and a transparent layer other than the special region is made of vitreous
silica whose raw material is primarily synthetic silica.

3. The vitreous silica crucible of claim 1, wherein the special region is
made from vitreous silica containing bubbles therein.

4. The vitreous silica crucible of claim 1, wherein the special region
has an uneven surface.

5. The vitreous silica crucible of claim 4, wherein the uneven surface is
comprised of a plurality of slits.

6. The vitreous silica crucible of claim 1, wherein the special region is
installed between 5 mm downward from an edge portion of an opening of the
vitreous silica crucible and 100 mm upward from the center of a bottom
surface of the vitreous silica crucible, and the special region has a
width ranging from 1 mm to 100 mm.

7. The vitreous silica crucible of claim 1, wherein the marking is a
laser marking.

8. The vitreous silica crucible of claim 1, wherein the marking is a
diamond tool marking.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a vitreous silica crucible for
pulling of silicon single crystals.

BACKGROUND ART

[0002] In the manufacturing of semiconductor devices, etc. used in
electronics technologies leading information-oriented society, silicon
wafers may not be omitted. Characteristics of silicon wafers include
micro defects such as oxygen precipitate, dislocation, oxygen stacking
faults and the like. Micro defects are advantageous for capturing heavy
metal pollution that occurs in a device process, but may become a source
of device failure. Therefore, there may be a need to adjust the oxygen
concentration in a crystal to a predetermined concentration corresponding
to types of devices or device processes used.

[0003] As a current method of manufacturing silicon single crystals, the
"Czochralski method" (hereinafter referred to as "CZ method") of
manufacturing silicon single crystals through pulling is generally used.
In addition, there is a method called the magnetic field applied
Czochralski method (MCZ method) which is a CZ method peformed under a
strong magnetic field. The CZ method includes a magnetic field applied
Czochralski (MCZ) method in which a strong magnetic field is formed.

[0004] In the CZ method, a polycrystalline silicon that is highly purified
with a metal impurity concentration of a few ppb (parts-per-billion, 1
ppb=10-9) or less is generally put into a high-purity vitreous
silica crucible together with a resistivity control dopant (e.g., boron
(B) or phosphorous (P)) and is melted at a temperature of about 1,420
deg. C. Continuously, a seed crystal silicon rod is brought into contact
with a surface of silicon melt, the seed crystal or the vitreous silica
crucible is rotated to make the seed crystal thin (dislocation-free) and
then the seed crystal is pulled, thereby enabling a silicon single
crystal ingot having the same atomic structure as the seed crystal to be
obtained.

[0005] As aforementioned, the vitreous silica crucible is a container to
put silicon melt therein when pulling molten polycrystalline silicon into
a single crystal. The amount of the silicon melt in the vitreous silica
crucible is decreased in inverse proportion to the amount of silicon
single crystal pulled, and the level of the surface of the silicon melt
(hereinafter referred to as "melt surface") is changed in the vitreous
silica crucible. It is general practice to directly observe and monitor
the changing level of the melt surface, but such direct observation has
the problem in that the decrease in volume of the silicon melt cannot be
accurately measured.

[0006] Recently, silicon single crystal ingots have been advanced to a
large diameter (of 300 mm or more). The large diameter of the silicon
single crystal ingot is problematic in that the phenomenon can easily
occur in which the melt surface of the silicon melt sloshes (vibrates)
between a portion where a neck part is formed and a portion where a
shoulder part is formed, for a duration of a few minutes to a few hours.
As a countermeasure to the foregoing problem, methods for preventing
vibration of the melt surface have been considered, such as a method of
applying a magnetic field to the melt surface through the foregoing MCZ
method, a method of providing a region, called a special region, in the
vitreous glass crucible for preventing the sloshing of the melt surface,
or the like. However, a method of completely preventing the vibration of
the melt surface under any pulling condition has not yet been found.
Therefore, even in the case where the melt surface is disposed in the
special region, a countermeasure that is employed is one where the
pulling rate is decreased during a period in which vibration of the melt
surface is easily generated.

[0007] In a conventional vitreous silica crucible, even though the
foregoing special region is provided, the special region cannot be
discerned by its appearance. Also, since a carbon susceptor supporting
the vitreous silica crucible reacts with an outer surface of the vitreous
silica crucible during the pulling of a silicon single crystal, so that
an inner diameter of the carbon susceptor is changed whenever the carbon
susceptor is used, initial melt surfaces are not always at the same
level, although silicon raw material is filled by the same weight in the
vitreous silica crucible. Therefore, although a distance between an
initial melt surface level and a melt surface level changed during
pulling is known, a relative position between the melt surface and the
special region provided in the vitreous silica crucible cannot accurately
be known.

[0008] That is, for example, although the sloshing of the melt surface
disappears, and the seed crystal arrives at a region beyond the special
region and may increase the pulling rate of a silicon single crystal, it
may not be determined whether the sloshing disappears due to an effect of
the special region or whether a region is one which may increase the
pulling rate, and in a real process, it is problematic that the pulling
rate of silicon single crystal may not be increased. In relation to this
problem, patent document 1 below discloses that a position measuring
apparatus is provided at a side of a single crystal pulling apparatus.

[0009] However, with the technique disclosed in the foregoing patent
document 1, although large-scale dedicated equipment is needed, only a
changed amount of the melt surface may be measured, and when a vitreous
silica crucible with a special region is used, if the vitreous silica
crucible is deformed during pulling of a silicon single crystal, the
positional relation between the melt surface and the special region may
not be found.

[0010] The present disclosure provides a vitreous silica crucible, which
has a special region for suppressing vibration of a melt surface during
pulling of a silicon single crystal and can accurately detect the
position of the melt surface and the position of the special region even
when the vitreous silica crucible is partially deformed due to the weight
of silicon melt or the like. The present disclosure also provides a
vitreous silica crucible provided with a marking, which can simply
realize an optimal pulling rate while suppressing vibration of a melt
surface during pulling of a silicon single crystal by accurately
detecting the position of the melt surface and the position of the
special region as above.

Means for Solving the Problems

[0011] The summarized configurations of the present invention are as
follows.

[0012] (1) A vitreous silica crucible for containing a silicon melt, the
vitreous silica crucible including: a special region provided on an inner
wall of a straight body portion, for preventing sloshing of the silicon
melt; and a marking installed at least at an upper end and a lower end of
the special region.

[0013] (2) The vitreous silica crucible described in the above (1),
wherein the special region is made of vitreous silica whose raw material
is primarily natural silica, and a transparent layer other than the
special region is made of vitreous silica whose raw material is primarily
synthetic silica.

[0014] (3) The vitreous silica crucible described in the above (1),
wherein the special region is made from vitreous silica containing
bubbles therein.

[0015] (4) The vitreous silica crucible described in the above (1),
wherein the special region has an uneven surface.

[0016] (5) The vitreous silica crucible described in the above (4),
wherein the uneven surface is comprised of a plurality of slits.

[0017] (6) The vitreous silica crucible described in any one of the above
(1) to (5), wherein the special region is installed between 5 mm downward
from an edge portion of an opening of the vitreous silica crucible and
100 mm upward from the center of a bottom surface of the vitreous silica
crucible, and the special region has a width ranging from 1 mm to 100 mm.

[0018] (7) The vitreous silica crucible described in any one of the above
(1) to (6), wherein the marking is a laser marking.

[0019] (8) The vitreous silica crucible described in any one of the above
(1) to (6), wherein the marking is a diamond tool marking.

Effect of the Invention

[0020] According to the present disclosure, for example, although the
vitreous silica crucible is deformed due to the mass of silicon melt
during pulling of a silicon single crystal, a change in position of the
melt surface with respect to a position of the special region can be
accurately detected. Therefore, directly after the melt surface has
passed the special region for preventing vibration of the melt surface,
it becomes possible to increase the pulling rate of silicon single
crystal, thereby contributing to the enhancement of productivity.

[0022] Hereinafter, exemplary embodiments will be described in detail with
reference to the accompanying drawings. Like reference numerals in the
drawings denote like elements, and thus their description will be
omitted.

[0023] A vitreous silica crucible is illustrated in a sectional view in
FIG. 1. The vitreous silica crucible 1 in accordance with an exemplary
embodiment is characterized by having a special region 2 provided on an
inner wall of a straight body portion 5, which is used in pulling of a
silicon single crystal by the CZ method or the like, to prevent a change
of a melt surface, and a marking 4 which is positioned at least at an
upper end and a lower end of the special region 2 and is detectable
(e.g., visually determinable (visually recognizable)) from an exterior of
a CZ furnace. Also, the vitreous silica crucible 1 in accordance with an
exemplary embodiment may be used in any of single pulling and multi
pulling methods.

[0024] First, the configuration of the vitreous silica crucible 1 will be
described. As illustrated in the sectional view of FIG. 1, the vitreous
silica crucible 1 includes the cylindrical straight body portion 5 having
a corner portion 9 with a relatively large curvature and an edge portion
of which the upper end is open, and a bottom portion 8 formed in a
straight line or a curved line having a relatively small curvature and
having a mortar shape. Also, in the description of the present
disclosure, the corner portion 9 is a portion connecting the straight
body portion 5 and the bottom portion 8, and denotes a portion from a
point where the tangent of a curved line of the corner portion 9 overlaps
the straight body portion 5 of the vitreous silica crucible to a point
having a common tangent to the bottom portion. The vitreous silica
crucible 1 has, from the inner side toward the outer side thereof, a
vitreous silica layer (hereinafter referred to as "transparent layer 6")
which does not substantially have bubbles (has a bubble content of less
than 0.5%), and a vitreous silica layer (hereinafter referred to as
"bubble containing layer 7") having a bubble content of from 0.5% or more
to less than 50%. In the description of the present disclosure, the
bubble content denotes the ratio (w2/w1) of a bubble occupying volume
(w2) to a constant volume (w1) of the vitreous silica crucible 1.

[0025] Next, a marking 4 position will be described. In FIG. 1, reference
numeral 1 is an edge portion of an opening of the vitreous silica
crucible, reference numeral 2 is the special region provided in an inner
wall of the crucible, for preventing sloshing of a melt surface,
reference numeral 3 is a center of the bottom portion, reference numeral
4 is the marking, and reference numeral 5 is a range (straight body
portion 5) in which the marking 4 is capable of being provided. In the
drawing, the range in which the marking 4 is capable of being provided is
preferably selected from the range of the straight body portion 5.

[0026] Herein, it is necessary to install the marking 4 at least at the
upper end and lower end of the special region 2. This is because the
marking 4 becomes a mark for confirming a change point in pulling
condition. In addition to the upper end and lower end of the special
region 2, the marking 4 may be provided at a position other than the
straight body portion 5, for confirmation of the melt content.

[0027] The special region 2 is, as described above, provided in the inner
wall of the vitreous silica crucible 1 to decrease the sloshing
(vibration) phenomenon of silicon melt when a silicon lump is made molten
and then pulled into a single crystal ingot. In this exemplary
embodiment, the special region 2 may be composed of natural vitreous
silica obtained by fusing natural silica, and the inner wall of the
transparent layer 6 of the vitreous silica crucible 1 other than the
special region 2 may be composed of synthetic vitreous silica.

[0028] Herein, it is meant that silica powder (synthetic silica powder)
for forming the synthetic vitreous silica is formed from synthetic
silica, and the synthetic silica is a raw material produced through
chemical synthesis. Since the raw material for the synthetic silica is
gas or liquid, it is possible to easily refine the synthetic silica, and
the synthetic silica powder may be prepared with a higher purity than the
natural silica powder. Also, the synthetic vitreous silica powder is
amorphous. As the raw materials for the synthetic vitreous silica powder,
there are gas raw materials such as carbon tetrachloride or the like, and
a silicon alkoxide liquid raw material. In the case of the synthetic
glass powder, it is possible to control all impurities at a concentration
of 0.1 ppm or less.

[0029] In the synthetic vitreous silica powder produced by a sol-gel
process, 50 ppm to 100 ppm of silanol generated by hydrolysis of alkoxide
remains typically. In the synthetic vitreous silica powder using carbon
tetrachloride as a raw material, it is possible to control silanol in a
wide range of 0 to 1000 ppm, but 100 ppm of chlorine is typically
contained. In the case of using alkoxide as a raw material, synthetic
vitreous silica powder which does not contain chlorine may be easily
obtained.

[0030] As aforementioned, the synthetic vitreous silica powder obtained by
the sol-gel process contains 50 ppm to 100 ppm of silanol before being
molten. When the synthetic vitreous silica powder obtained by the sol-gel
process is molten in vacuum, separation of silanol occurs and thus
silanol content in the synthetic vitreous silica obtained is decreased to
5 ppm to 30 ppm. Also, the silanol content may be different depending on
fusing conditions such as fusing temperature, elevation temperature, etc.
In addition, silanol content in the natural vitreous silica obtained by
fusing natural silica powder under the same condition is 50 ppm or less.

[0031] Generally, it is known that synthetic vitreous silica is lower in
viscosity at a high temperature than natural vitreous silica obtained by
fusing natural silica powder. As one such reason, it may be considered
that silanol or halogen cuts the network structure of SiO4
tetrahedron.

[0032] From the measurement of the transmittance of the synthetic vitreous
silica obtained by fusing synthetic vitreous silica powder, it can be
understood that the synthetic vitreous silica well transmits ultraviolet
rays having a wavelength of up to about 200 nm, and has a similar
characteristic to the synthetic vitreous silica which is obtained from a
raw material of carbon tetrachloride and is used for ultraviolet optical
purposes.

[0033] Also, in the case of the synthetic vitreous silica obtained by
fusing synthetic vitreous silica powder, when a fluorescent spectrum as
excited to ultraviolet rays having the wavelength of 245 nm is measured,
the fluorescent peak which is the same as that of a product obtained by
fusing natural silica powder cannot be observed.

[0034] The natural silica powder indicates that the natural silica powder
is prepared from natural silica, the natural silica is a raw material
obtained through crushing, refinement and the like of naturally occurring
silica gemstone, and the natural silica powder is obtained from
α-quartz crystal. The natural silica powder contains Al and Ti of 1
ppm or more, and other impurities having a higher concentration that
those contained in the synthetic silica powder. The natural silica powder
contains almost no silanol. The silanol content in the natural vitreous
silica obtained by fusing the natural silica powder is less than 50 ppm.

[0035] From the measurement of the transmittance of glass obtained from
the natural silica powder, it can be seen that the transmittance is
sharply decreased at a wavelength of 250 nm or less due to about 1 ppm of
Ti mainly contained as an impurity, and approaches almost zero at a
wavelength of 200 nm. Also, an absorption peak due to an oxygen defect
can be seen at a wavelength of around 245 nm.

[0036] Additionally, from the measurement of a fluorescent spectrum
obtained when a fused product of the natural silica powder is excited at
the wavelength of 245 nm, fluorescent peaks are observed at the
wavelengths of 280 nm and 390 nm. These fluorescent peaks are due to an
oxygen bond defect in glass.

[0037] By measuring any of a concentration of a contained impurity,
silanol content or transmittance, or by measuring a fluorescent spectrum
obtained when a measurement target is excited by ultraviolet rays of 245
nm, it can be determined whether vitreous silica of the measurement
target is made of natural silica or the synthetic silica.

[0038] During the fusion of the silica powder layer, the transparent layer
6 may be produced from the mold by decreasing the pressure to -50 kPa or
more to less than -95 kPa. Also, after the transparent layer 6 is formed,
the bubble containing layer 7 may be formed on an outer side of the
transparent layer 6 by adjusting the pressure to +10 kPa to less than -20
kPa. At this time, in a region where the special region 2 should be
formed, by providing a silica powder layer having the natural silica as a
main component (e.g., natural silica/synthetic silica=2/1) as an inner
layer and then fusing the silica powder layer while decreasing the
pressure as above, the special region 2 may be easily formed. Also, in a
region other than the region where the special region 2 should be formed,
it is good to provide a silica powder layer having the synthetic silica
as a main component as an inner layer and then melt the silica powder
layer while decreasing the pressure as above.

[0039] While the synthetic and natural silica powders are used as raw
materials in this exemplary embodiment, the "silica powder" referred in
the description of the present disclosure is not limited to quartz
powder, and may include conventionally well known material powders such
as crystal, silica or the like including silicon dioxide (silica) as raw
materials of the vitreous silica crucible if the foregoing conditions are
satisfied.

[0040] Also, the special region 2 in accordance with the exemplary
embodiment may be composed of vitreous silica containing bubbles therein.
Additionally, in case of providing the special region 2 to a typical
vitreous silica, it is good to provide an uneven surface to the special
region 2. Additionally, the uneven surface may have a structure comprised
of a plurality of slits.

[0041] The special region 2 will be described in more detail. In the
exemplary embodiments of the present disclosure, methods of providing the
special region 2 which are described below are not limited, and any of
conventional methods of providing the special region 2 which are well
known to prevent vibration of silicon melt may be used properly. A first
method is the special region obtained from a raw material having natural
vitreous silica as a main component, as aforementioned. An existence
region of the natural vitreous silica has a thickness of about 2 mm from
an inner wall and a width of, suitably, 100 mm or less, and more
preferably, of about 30 mm in the height direction. Also, in the
exemplary embodiment of the present disclosure, the layer having natural
vitreous silica as a main component indicates a vitreous silica layer
obtained from a raw material powder having a ratio of natural silica
powder mass/synthetic silica powder mass being equal to 1 or more.

[0042] A second method is the special region 2 obtained from a vitreous
silica containing bubbles therein. In the exemplary embodiment of the
present disclosure, the bubbles refer to bubbles (having a diameter of
about 5 μm or more) detectable with the naked eye by using light
scattering. That is, the mean-diameter of the bubbles is preferably in
the range of 5 μm to 50 μm, more preferably, in the range of 10
μm to 40 μm, and even more preferably, about 30 μm. Also, the
existing density of the bubbles is preferably 10/cm2 or more, more
preferably, 20/cm2 or more, even more preferably, 30/cm2 or
more, and still more preferably, about 40/cm2. Also, the existing
density of the bubbles is preferably 100/cm2 or less, and more
preferably, 70/cm2 or less. Also, the thickness of the special
region 2 is preferably 1 mm or more from an inner wall, and more
preferably about 2 mm. The width in the height direction of the special
region 2 is preferably less than 100 mm, and more preferably, about 40
mm. Also, the width in the height direction of the special region 2 is
preferably 1 mm or more, and more preferably, 10 mm or more.

[0043] A third method is the special region 2 characterized by having an
uneven surface. The characteristic of the uneven surface is preferably a
ten-point mean roughness (Rz) of 0.1 mm or more, more preferably, 0.3 mm
or more, and even more preferably, about 0.5 mm. Also, the mean roughness
of the uneven surface is preferably 1.0 mm or less, and more preferably,
0.7 mm or less. Additionally, the width in the height direction of the
special region is preferably within 100 mm, and more preferably, about 40
mm. Also, the width in the height direction of the special region 2 is
preferably 1 mm or more, and more preferably, 10 mm or more. In the above
description, the surface indicates the inner wall surface of the vitreous
silica crucible 1.

[0044] A fourth method is the special region 2 characterized by having the
uneven surface comprised of a plurality of slits. The characteristic of
the slits is preferably a mean length of 10 mm or more, more preferably,
30 mm or more, and even more preferably, about 50 mm. Also, the
mean-length of the slits is preferably 100 mm or less, and more
preferably, 70 mm or less. The mean-width of the slits is preferably 0.1
mm or more, more preferably, 0.3 mm or more, and even more preferably,
about 0.5. Also, the mean-width of the slits is preferably 1.0 mm or
less, and more preferably, 0.7 mm or less. Additionally, the mean-depth
of the slits is preferably 0.1 mm or more, more preferably, 0.3 mm or
more, and even more preferably, about 0.5 mm. Also, the mean-depth of the
slits is preferably 1.0 mm or less, and more preferably, 0.7 mm or less.
Also, the existing density of the slits is preferably 5/cm2 or more,
more preferably, 10/cm2 or more, and even more preferably about
20/cm2. Also, the existing density of the slits is preferably
50/cm2 or less, and more preferably, 30/cm2 or less. Also, the
width in the height direction of the special region 2 is suitably within
100 mm, and more preferably, about 40 mm. Also, the width in the height
direction of the special region 2 is preferably 1 mm or more, and more
preferably, 10 mm or more.

[0045] As exemplarily illustrated in FIG. 1, a position where the special
region 2 is installed is preferably between 5 mm in the downward
direction from an upper end of an opening of the vitreous silica crucible
and 100 mm in the upward direction from a center of the bottom surface of
the crucible, and more preferably, between 10 mm in the downward
direction from an upper end of an opening of the vitreous silica crucible
and 200 mm in the upward direction from a center of the bottom surface of
the crucible. The width in the height direction of the special region 2
is preferably in the range of 1 mm to 100 mm. In the exemplary embodiment
of the present disclosure, the height direction indicates an arrow
direction in FIG. 1.

[0046] The shape of the marking 4 is a point (circle) or line (rectangle),
and it is good that the number of points, the length of lines, etc. are
observed while directly watching the marking 4 during pulling of a
silicon single crystal (or are detected by using an optical measurement
apparatus or the like), and are properly selected corresponding to the
visibility of the real CZ furnace. For example, in the case of the
points, the depth of each point is preferably half or less of the
thickness of the vitreous silica crucible 1 at a depth of 0.1 mm or more,
and more preferably 1/3 or less of the thickness of the vitreous silica
crucible 1 at a depth of 0.2 mm or more. Also, the diameter thereof is
preferably 0.5 mm or more, more preferably, 0.7 mm or more, and even more
preferably, about 1 mm. Also, the diameter thereof is preferably 3.0 mm
or less, and more preferably, 2.0 mm or less. Additionally, in the case
of the lines, the depth of each line is preferably half or less of the
thickness of the vitreous silica crucible 1 at a depth of 0.1 mm or more,
and more preferably 1/3 or less of the thickness of the vitreous silica
crucible 1 at a depth of 0.2 mm or more. Also, the width thereof is
preferably 0.5 mm or more, more preferably, 0.7 mm or more, and even more
preferably, about 1 mm. Also, the width thereof is preferably 3.0 mm or
less, and more preferably, 2.0 mm or less. Additionally, the marking 4 is
not necessarily needed to exist throughout the whole circumference of a
horizontal surface of the vitreous silica crucible 1, but is preferably
provided with a length of about 5 cm or more, and more preferably with
the length of 10 cm or more.

[0047] The marking 4 in accordance with the exemplary embodiments of the
present disclosure may be needed to be provided at least at an upper end
and a lower end of the special region 2 because of the foregoing reason.
At this time, since the marking 4 in the upper end does not contact the
silicon melt almost or completely during pulling of a silicon single
crystal, it is not so necessary to consider a decrease in the thickness
of the vitreous silica crucible 1 itself.

[0048] Meanwhile, since the marking 4 in the lower end contacts the
silicon melt, it is necessary to consider a decrease in the thickness of
the vitreous silica crucible 1 itself.

[0049] In addition to the upper end and the lower end, the marking 4 in
accordance with exemplary embodiments of the present disclosure may be
provided between the upper end and the lower end, or at a lower position
of the lower end. That is, in the case where the marking 4 is provided
between the upper end and the lower end of the special region 2, the
marking 4 may be used as a start point in the step of changing pulling
conditions of a silicon single crystal. Also, in the case where the
marking 4 is provided at the lower position of the lower end of the
special region 2, the marking 4 may be used as a reference for detecting
the remaining content of the silicon melt.

[0050] It is important that the marking 4 used in exemplary embodiments of
the present disclosure is formed at a correct position with respect to
the special region 2 and is visually recognizable (or detectable). The
marking 4 is preferably a laser marking formed by a laser or a diamond
tool marking formed by a diamond tool. In addition to the foregoing
marking methods, all conventional well known marking methods, a marking
using a very rigid drill or the like may be applied if such tools can
form the marking 4 in silica materials. That is, the marking method is
selected by the depth or length of the marking 4, but from among the
foregoing marking methods, it is preferable to provide the marking 4 by
using the foregoing diamond tool or laser, and in particular, a CO2
gas laser.

[0051] Also, a well known diamond tool may be properly selected as the
diamond tool used in the exemplary embodiments of the present disclosure
by the shape of the marking 4. For example, the well known diamond tool
may include a diamond wheel, a diamond tipped drill, or the like.

[0052] The forming of the marking using the diamond tool may be performed
according to the following process.

1. Process of loading a crucible on a bottom plate having an opening for
marking at a center thereof with a three-jaw scroll chuck tool for
determining a central position of the crucible such that the opening of
the crucible is directed toward the downward direction. 2. Process of
determining the central position of the crucible with the three-jaw
scroll chuck tool. 3. Process of elevating a diamond tool processor to an
inner wall of the crucible. 4. Process of controlling a processing
position. 5. Process of providing a marking with the diamond tool. 6.
Process of sequentially and repeatedly forming a marking while the bottom
plate having a servo controller rotates. 7. Process of returning the
diamond tool processor to the original position.

[0053] While the embodiments of the present disclosure have been
particularly shown and described with reference to the accompanying
drawing, it will be understood by those of ordinary skill in the art that
the embodiments are only examples and various changes in form and details
may be made.

[0054] For example, in the case of the special region 2 primarily made of
natural silica as illustrated in FIG. 1, the marking 4 in accordance with
the exemplary embodiments of the present disclosure may be provided along
the whole circumference of the crucible or along a portion of the
circumference of the crucible.

EXAMPLES

[0055] Hereinafter, the present invention will be further described with
Examples thereof, but the present invention is not limited to the
Examples.

Example 1

[0056] A marking in accordance with Example 1 was formed in the following
sequence in a vitreous silica crucible of about 800 mm in diameter, which
was manufactured by a conventional well known method. The formed marking
was a pointed shape of which the diameter is 1 mm. Also, in the present
Example, a special region primarily made of natural silica (natural
silica/synthetic silica=2/1) and having a width of 30 mm in the height
direction and a depth of 100 μm was formed in the vitreous silica
crucible.

[0057] [Laser Marking Sequence]

1. Process of loading a crucible on a bottom plate having an opening for
marking at a center thereof with a three-jaw scroll chuck tool for
determining a central position of the crucible such that the opening of
the crucible is directed downward. 2. Process of determining the central
position of the crucible with the three-jaw scroll chuck tool. 3. Process
of elevating a laser processor to an inner wall of the crucible. 4.
Process of controlling a distance between the inner wall of the crucible
and a laser irradiation hole with a red semiconductor laser, equipped
with the laser processor having a wavelength of 650 nm. 5. Process of
providing a marking with the laser. 6. Process of sequentially and
repeatedly forming a marking while the bottom plate having a servo
controller rotates. 7. Process of returning the laser processor to the
original position.

[0058] Also, the irradiation conditions of a CO2 gas laser are as
follows:

[0060] As a result of forming the marking in accordance with Example 1
with the above irradiation conditions, the special region primarily made
of natural silica was visually observed properly.

Example 2

[0061] Next, the crucible used in Example 1 was heated to 1400 deg. C. to
intentionally deform the crucible. When the laser marking was formed in
accordance with Example 1, the special region primarily made of natural
silica was visually observed accurately even when the crucible was
deformed.

Example 3

[0062] The crucible used in Example 1 was loaded on a carbon susceptor
having a spacing of about 7 mm at a corner portion, about 80 kg
polycrystalline silicon was put in the crucible, the crucible was
installed in a CZ furnace, the polycrystalline silicon in the crucible
was molten at about 1450 deg. C. and maintained for 20 hours. The special
region was visually observed from an exterior of the CZ furnace, and the
special region primarily made of natural silica was visually observed
accurately. After the crucible was cooled to room temperature, the
spacing between the vitreous silica crucible and the carbon susceptor as
measured was 2 mm, indicating a large deformation of the crucible. That
is, even though the corner portion of the crucible was deformed by about
5 mm, the special region primarily made of natural silica in the vitreous
silica crucible having the marking formed in accordance with Example 1
was observed accurately.

Example 4

[0063] Vitreous silica crucibles having the same specification as that in
Example 1 were prepared. Some of the prepared crucibles were processed to
have a laser marking formed in the conditions of Example 1, but the other
as a comparative example was not processed. The respective crucibles were
installed in the CZ furnace. A polycrystalline lump of about 100 kg was
put in each of the vitreous silica crucibles, the CZ furnace was
maintained in an argon gas atmosphere (at a pressure of 6.67 kPa) and was
elevated in temperature from room temperature (20 deg. C.) to 1500 deg.
C. for 10 hours, the elevated temperature was maintained for a
predetermined time to melt the polycrystalline silicon lump and thus form
silicon melt such that the melt surface of the silicon melt was
positioned at the special region. At this time, in the vitreous silica
crucible formed with the laser marking in accordance with the embodiment
of the present invention, the marking in the upper end was observed, but
the marking in the lower end was not observed due to the silicon melt. A
seed crystal was dipped in the silicon melt prepared as above and then
gradually pulled while rotating the crucible, to grow a silicon single
crystal with a diameter of 400 mm and length of 0.3 m in a condition that
the sloshing of the silicon melt is minimized.

[0064] When the conventional vitreous silica crucible not having a marking
was used, 17 hours were taken for pulling. In contrast, when the vitreous
silica crucible formed with the marking in accordance with embodiments of
the present disclosure was used, the pulling rate was increased from 0.3
mm/min to 0.6 mm/min, and thus only 15 hours were taken for pulling. Due
to the effect of the laser marking described with the embodiments of the
present disclosure, it was confirmed that the productivity was enhanced
by 10% or more. In both of the inventive example and the comparative
example, the crystallization rate was 100%.

[0065] While the present invention has been particularly shown and
described with reference to exemplary Examples thereof, it will be
understood by those of ordinary skill in the art that various
modifications will be possible and such modifications will be construed
as being included within the scope of the invention.

[0066] For example, while in the Examples of the present disclosure, the
laser marking is recognized by direct observation with the naked eye, the
present invention is not limited thereto. That is, the position of the
laser marking may be detected by using an optical measurement apparatus
instead of direct observation.

INDUSTRIAL APPLICABILITY

[0067] Since the present invention can accurately and easily use the
special region which is effective in preventing vibration of silicon melt
surface in the vitreous silica crucible containing silicon melt in the
pulling of a silicon single crystal using the CZ method, it becomes
possible to efficiently perform the pulling of silicon single crystal
using the CZ method. As a result, a high quality silicon single crystal
ingot can be manufactured in a shorter time than in the conventional case
and at an optimal pulling rate.